From a seminal turn on Superboy and the Legion of Super-Heroes and creating the lost world of the Warlord, to his work on Green Arrow--first relaunching the Green Lantern/Green Arrow series with Denny O'Neil, and later redefining the character in Green Arrow: The Longbow Hunters--Mike Grell made an indelible mark at DC Comics in the 1970s and '80s. But his greatest contribution to the comics industry was in pioneering creator-owned properties like...